Semiconductor devices, such as diodes and transistors are essential components for electronic devices. A continuing demand exists for new, alternative, less expensive and/or improved manufacturing processes for their production.
Currently, a particular interest exists in processes for the production of flexible electronics components for use e.g. in RFID tags, flexible LED and LCD displays and photovoltaics. Flexible electronics are typically produced using so-called roll-to-roll (R2R) processing (also known as web processing or reel-to-reel processing). R2R processing refers to production methods wherein thin-films are deposited on a flexible (plastic) substrate and processed into electrical components in a continuous way.
In an R2R process preferably printing techniques (e.g. imprint, inkjet, or screen printing) and coating techniques (e.g. roll or spray coating) are used in order to achieve a high throughput, low-cost processing. Such techniques include the use of inks, i.e. liquid compositions, which can be deposited on the substrate using a simple coating or printing technique. This way flexible electronics can be fabricated at a fraction of the cost of traditional semiconductor manufacturing methods. R2R processing is however a technology which is still in development.
Problems that need to be overcome in order realize flexible electronics for high-performance applications, such as HF RFIDs and electronics for foldable phones, include the development of low-cost processes for the realization of thin-film structures with small feature size and high alignment accuracy and the development of ink-based processes for realizing high-mobility semiconducting thin-films on a flexible plastic substrate.
U.S. Pat. No. 6,861,365 B2 describes the realization of a three-dimensional resist structure on a thin-film semiconductor multi-layer stack on a flexible substrate. Subsequent (anisotropic) etching of the 3D mask allows the formation of thin-film semi-conducting structures in the multilayer stack. The minimum feature size and the alignment accuracy are determined by the 3D mask, which is further determined by the photolithography. The etching steps however are based on vacuum process thus providing a R2R process with an inefficient energy consumption and material usage. Moreover, although the 3D resist mask provides the required alignment, it introduces substantial design constrains and processing complexity.
EP 1 087 428 A1 describes a method for forming silicon film on the basis of silicon-containing ink. A solution containing a silane compound is applied onto a quartz substrate using ink-jet printing. After evaporation of the solvent, a silicon precursor film is formed that is subsequently transformed in silicon by an annealing step. The method however requires very high temperatures of up to 550° C. for converting the silane compound in the film into a crystalline silicon. Such high temperatures processing steps cannot be used in combination with flexible plastic substrates.
Hence, there is a need for in the art for improved methods for manufacture of thin-film structures on a flexible plastic substrate.